CA2013310A1 - Damping compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process of using compositions comprising certain thermoplastic elastomeric polymers for damping and damping compositions comprising soft thermoset polymer containing microscopically discrete segments of said thermoplastic elastomeric polymers.

Description

2~1 ~"3 ~ ~3 NOVEL DAMPING COMPOSITIONS

BACKGROUND OF THE INVENTION

1. Fiel~ he lnvqQtiQn This invention relates to the use of a certain multi-phase, thermoplas~ic elastomeric polymer for damping purposes, and new damping compositions comprising said polymer.
2. Description of the Prior Art Lorentz et al., pps. 306 - 329, in Piirma and Gardon, ed., rEmulsion Polymerization", American Chemical Society Symposium Series 24, Washington, DC, 1976, and Sperling, pps. 21 -56, in Paul and Sperling, ed., "Multicomponent Poiyme~ic Matefials", American Chemical Society Symposium Series 211, Washington, DC, 1986, have discussed in detail the damping properties of two-phase emulsion polymers of varying composition wherein the second polymer is polymarized in the presence of the first.

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Lohr, U.S. Patent 3,430,902 teaches a vibration damping device comprising a solid, high molecular weight amorphous polymer utilized at or near its glass temperature combined with means for heating or cooling so that the glass temperature is approximately that of the use temperature of the vibration support.
Tabar et al. U.S. Patent 4~362,~ and U.S. Patent 4, 419,480; ^
Lemieux et al., Rubber Chem. Tech., 57, 792 (1984~; Mæich et al. ibid., ~, 623 (1986) teach soft compositions useful as low modulus, high damping, high fatigue life elastomer compounds for vibration isolation.
The compounds are cured, vulcanized, or crosslinked blends of natural rubber with bromobutyl rubber to which has been added a non-vulcanizable polyisobutylene which remains in a discrete phase after cure; a particulate additive such as carbon black is also incorporated. These two patants also teach the use of synthetic poly(isoprene) or polybutadiene in simil~r l~nds to improve the heat resistanceoftheblend. C~ j2~J 1~
Falk et al, U.S. Patent 4,473,679, claim thermoplastic core-shell compositions having a rigid core surrounded by a rubbery acrylic partially encapsulatin~ layer, with a copolymeric transition layer formed from the mixture of monomers used to prepare the core and shell layer.
Makati et al, U.S. Patent 4,717,750 and U.S. Patent 4,742,108;
Lee et al., U.S. Patent 4,569,964 teach reinforced latex particle structures. The Makati et al. patents teach a second phase of glass temperature higher than either the first or third phase.

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Hofmann, US Patent 4,180,529, teaches a four-phased emulsion polymer having a non-elastomeric second phase which may contain up to 5% of a crosslinking monomer in combination with a alastomeric first phase. Owens, US 3,793,402 teaches a similar staging with an additional thermoplastic outer phase.
The Derwent abstract of Japanese Patent 79-84g7 teaches blends of liquid thermosetting resins with rubbery polymers and linsar thermoplastic resins as vibration-reducing materials useful at high temperatures and flexible at ordinary temperature.
The Derwent abstract of Japanese Patent 88-1979 teaches blends of natural rubbcr with a solubls chloromethylstyrene-butadiene-styrene terpoiymer as a useful hi~h modulus 01astomeric product.
Frankel ~t al. European Patent Application 187,505, published July 16, 1986, teach two-phase polymers used in the present invention.
Sugii et al. (Nitto Electric) in Japanese Kokai 60-92372 t~ach a polymer useful as an improved pressure sensitive adhesive by first polymerizing a (meth)acrylic polymer which produces a tacky material, adding a monomer mixture enriched in a multifunctional monomer, along with an organic peroxide, to swell the particles and conducting the polymerization of the second monomers at an elevated temperature.

$UMMARY OF THE !~JYE~LII~I
The present invention is directed to a process which comprises using a certain multi-phase thermoplastic elastomeric polymer for damping, i.e., as a damping material. The muiti-phase polymer has at least two polymeric phases: (a) an in~tial (I.e. first) linear or lightly crosslinked polymeric phase polymerized from an a, B ethylenically unsaturated monomer, wherein the o~, ~ ethylenically unsaturat~d monomer comprises from about O to about 2% by weight of multi-ethylenically unsaturated monomer, and (b) a second polymeric phase in the form of discrete domains of about 2 to about 15 nm in diameter dispersed within the initial polymeric phase, wherein the second polymeric phase is polymerized from at least one ethylanically unsaturated monomer comprised of about 5% to 100% by weight multifunctional monomer having at least two sites of ethylenic unsaturation. The waight ratio of the second polym0ric phase tc the initial polymeric phase plus said second polymeric phase is from about 1 :100 to about 1:2. The multi-phase polymer may ~urther comprise a final (i.e., third) polymeric thermoplastic phase whose glass transition temperature is greater than that of the initial polymeric phase, a portion of the final polymeric phase being intimately attached to at least one of the initial or second polymer phases.
Accorciing to another aspect of this invention, it is directed to a composition us~d for damping which comprises: (a) soft crosslinked elastomer containing (b) microscopically discrete segments of the multi-phase, thermoplastic elastomeric polymer disclosed above. The elastomer is crosslinked with (d) curative in an amount sufficient to crosslink the elastomer.
According to another aspect of the invention, it is directed to the use of such composition for damping purposes.
An obiect of the present invention is the use of a muiti-phase polymer of certain morphology which exhibits excellent damping behavior over a broad temperature range.

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Another object of this invention is the combination of these multi-phase polymers as microscopically discrete segments with a thsrmosettable or vulcanizable elastomer or elastomer blend to yield a composition having excellent damping, good resistance to fatigue failure, and resistance to creep. It is a further object to provide such compositions which are readily processible and remoldable. It is a further object to provide a damping composition which provides outstanding damping performance over a wide range of use temperatures. It is a further object to provide such compositions as useful damping elements for vibration isolation in computers, motors, automotive and truck components, such as steering column connectors.
power generators, or rubber sheeting for vibration isolation of computers, audio equipmsnt, and the like.
These objects and others as will become apparent from the following disclosure are achieved by the present invention.

DETAILED DESCRIPTION OF THE INVENTION AND
THE PREFERRED EMBODIMENTS

Damping is the absorption of mechanical energy by a material in contact with the source of that energy. It is desirable to damp or mitigate the transmission of mechanical energy from, e.g., a motor, engine, or power source, ts its surroundings. Elastomeric materials are oft~n used for this purpose. It is desirabls that such materials be highly effective in conv0rting this mechanical energy into heat rather than transmitting it to r~

the surroundings. It is further desirable that this damping or conversion is effective over a wide range of temperatures and frequencies commonly found near motors, automobiles, trucks, trains, planes, and the like.
A convenient measure of damping is the determination ot a parameter call~d tan 8 . A forced oscillation is appliad to a material at frequency f and the transmitted force and phase shift are measured. The phase shift angle delta is recorded. The value of tan ~ is proportional to the ratio of (energy dissipatcd)/(energy stored). The measurement can be made by any of several commercial testing devices, and may be made by a sweep of frequencies at a fixed temperature, then repeating that sweep at sevoral other ternperatures, followod by the development of a master curve of tan ~ vs. frequency by curve alignment. An alternate mcthod is to measure tan 8 at constant frequency (such as at 10 hz) over a temperature range.
We have defined a thermoplastic unfilled material as useful for damping wh0n tan ~ ~ 0.4 over at least a 4 decade range, preferably a 6 decade range of frequency.
It is further important that this high degree of absorption of energy be accompanied by good mechanical and thermal stability, as the part prepared from 1he subject polymers will be cycled through various environments and repeatedly such to various forces of compression, tension, bending, and the like.

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The thermoplastic elastomeric polymers described by Frankel et al, U. S. serial number 683,~02, filed 12/20184, continuation application 92,816 filed 913187, are usaful in the process and compositions of this invention. This reference is hereby exprsssly incorporated by references for such teachings.
Also useful in the present invention are three-phase polymers in which up to about 20% by weight of a third or of a final phase is polymefized in tha prasence of two-phase polymers as described by Frankel et al. The final polymeric thermoplastic phase is selected to have a glass temperature greater than that of the initial polymeric phase, and a portion of the final polymeric phase will be intimately attached to the initial and/or the second polymer phases.
The first phase polymer may contain small amounts, up to about 10%, of certain polar or functionalized monomers. Preferred are acids, such as acrylic, methacrylic, isoascorbic, maleic, fumaric, and the like or nitrils-containing monomers, such as acrylonitrile, methacrylonitrile, beta-cyanoethyl acrylate, and the like. Espacially preferred is acrylic acid in amounts from about 2 to about 4 percent. Also especially preferred is acrylonitril0 in amounts from about 2 to about 7 percent.
It is also preferr~d that the molecular weight of the first phase be high. Use of mercaptan to lower molecular weight of the first phase should be avoided. Polymefization at low temperatures, such as below about 65, is preferred.
It may be desirable to lower the glass temperature of the first phase polymer. Such may be accomplished by lowering the amounts of lower alkyl methacrylate copolymerized or by use of an acrylate rnonomer with a longer side chain, such as 2-ethylhexyl acrylate. The third phase polymers preferably con~ain mers which are predominately (meth3acrylic esters, and the hardness of the third phase may be controlled by the nature of the copolymer formed. It is preferred that the polymer be about at least 50% lower alkyl methacrylate to about 100%
lower alkyl methac~late, the lower alkyl methacrylate being preferably methyl methacrylate, and from about 0 to about 59% of one or more lower alkyi acrylates. Other monomers, such as styrene, other alkyl methacrylates, other alkyl acrylates, acrylonitrile, atc., may be present in amounts up to about 20%. Specific functionalized monorners, such as acrylic acid, msthacrylic acid, acryloxypropionic acid, dimethylaminoethyl methacrylate, and the like, may be present in amounts up to about 5% of the third phase monomer mixture, as also may be monomers useful in promoting adhesion to metal, wood, glass, or polymeric substrates, such as those containing ureido or glycidyl functionality.
It is preferable that little or no new emulsifier be added during the formation of the third phase polymer. Initiators as taught in Frankal et al.
may be utilized. It may be desirable to incorporate a chain transfer agent with the third phase monomers. Preferred are primary, secondary or tartiary alkyl mercaptans, especially longer alkyl mercaptans, such as n-dodecyl or t-dodecyl. Other mercaptans, such as thioglycolate or mercaptopropionate esters, may be used, as may other well-known transfer agents such as bromotrichloromethane. Such may be added directly with the third phase monomers or separately before or during the third phase polymerization.
The polymer emulsion may be agglomerated or aggrsgated by techniques described in the literature so as to increase the particle size.
Such agglomeration may be accomplished by pH adjustment, by partial coagulation, and the like. Agglomeration may be accomplished prior to or after final staging.
Particulate fillers such as carbon black, mica, talc, and the like may be introduced into the multi-phase polymers at either the extrusion/isolation step or the isolated polymer may be re-processed to incorporate the filler, by means such as milling on a two-roll mill. Levels of fjIIQr may be as high as about 40%. Preferably such particulate fillers are reinforcing particulate flllers.
The multi-phase polymers may be converted into articies useful for damping by known molding or extrusion techniques. Both inJection molding and compression molding may be employed. Useful articles include solid supports, gaskets, bushings, interlinsrs, and the like.
These muHi-phase polymers are also described herein as thermoplastic elastomeric polymers, as they are both thermoplastic, in that they can bH molded and re-processed as true thermoplastics, yet exhibit an elastomeric r~sponse to stress, as well as the noted absorption of mechanical ener~y.
In addition to their use in their own right as articles useful for damping, the multi-phase polymcrs may be combined into thermoset elastomer(s) systems (i.e., elastomer, curative, fillers, ~tc.) to enhance damping performance thereof. The resulting thermoset compositions are fatigue resistant and may be shaped during the curing process into useful articles, such as gaskets, motor mounts, bushings, sheets, and the like. Such compositions are especially ussful in damping vibration from motors, engines, and other mechanical components, as well as vibrations resultiny from vehicular or other motion in buildings, electronic and mechanical equipment, and the like. They are especially useful In situations wher~ heat and repeated vibration can cause fatigue impairment of the long-term prop~rties of other elastomer. The acrylic muiti-phase polymers are especially useful in their resistance to heat and oxidative degradation and oil swelling. Where heat resistance of the composition is desired, polymers of butadiene are preferably included in the composition as a crosslinkable elastomer.
The thermoset elastomers may be based on any of a number of crosslinkable elastomers, such as polymers or copolymers of butadiene, ethylene-propylene-diene terpolymers, acrylic ester copolymers containing cure sites, polymers of isoprene, polymers of isobutylene containing unsaturation for curing, curable urethane elastomers, polymers from chloroprene monomer, anci the like. Preferred are bromobutyl rubber, elastomeric polybutadiene, and polyisoprene;
aspecially preferred are blends of natural or synthetic polymers of isoprene with bromobutyl rubber in ratios of from about 10/90 to about 90/10 parts by weight.
The Tab~r et al. pat~nts teach curatives, fillers, and the like and methods for combining the materials of the crosslinkable ~lastomer systems, curing same, and physical testing thereof. These patents are hereby expressly incorporated by reference for such teachings. In those patents, strain crystallizable isobutylene polymers are taught as softening materials when added in fatigue enhancing amounts. The formulations and techniques for processing such systems are directly applicable to those used for the processing of cGmposition comprising curable nubber with the thermoplastic multi-phase acrylic polymers of the presant invention, except for the replacement of the polyisobutylene. Thus, a preferr0d amount of thermoplastic multi-phase polymer included in the natural rubber/bromobutyl rubber blends is from about 10 parts to about 40 parts per 100 parts o~ crssslinkable elastomer blend. An especially preferred amount is from about 10 to 30 parts of multi-phase polymer per 100 parts of crosslinkable elastomer.
The crosslinkable elastomer may preferabiy be crosslinked by a curative comprising a curing agent selected from the group consisting of:
a) a sufficisnt amount of sulfur to provide an efficient or semi-efficient crosslinking of the soft thermosat composition; b) isocyanate or blocked isocyanate in an amount sufficient to crosslink the elastomer. The use of sulfur is espacially preferred.

EXAMPLES
The examples are intended to illustrate the present invention and not to limit it except as it is limited by the claims. All temperatures are in degrees Celsius. All percentages are by weight unless otherwise specified, and all reagents are of good commercial quality unless otherwise specified.
Standard procedures are used to characterize the emulsions.
Particle sizes are determined by a quasielastic light scattering technique using a Nano-Sizer~ particle size analyzer manufactured by Coulter Electronics Inc. The procedures used to deterrnine soluble fraction and gel sw011 ratio as given below.
The soluble fraction and gel swell ratio are polymer charactaristics which are determined using acetons as the solvent. A known weight of polymer (either as the emulsion or as the isolated polymer) is placed in a centrifuge tube along with about 50 times the polymer weight of acetone (e.g., 0.5 ~ of polymer in 25 g aceton~ in a 50 ml. tube). After shaking, usually ov~rnight, the sample is centrifuged (20,000 rpm for 60-90 min.) to precipitate the insoluble gsl. The clear supernate is removed and dried to determine soluble polymer. The gel is redispersed in acetone for at least 4-6 hours and centrifuged again. The clear supernate is removed and dried as before. If the second extra~ion gives more ~han about 5% soluble fraction, th~ extraction is repeat~d until l~ss than about 5% is found in the supernate. The weights of the polymer in the soluble fractions are summed and the percent soluble fraction is calculated as (weight of soluble polymer/total polymer weight) X 100.
After the last extraction, the weight of the acetone swollen gel is determined and the gel swell ratio calculated as weight of wet gel divided by (total polymer weight - soluble polymer weight).
All milling and molding for Examples 1-6 were performed at 177C. The tensile and elongation measurements were performed according to ASTM-D-882; the Tg measurements according to ASTM-D-3418-75 on a Perkin-Elmer DSC-2.
The following abbreviations ara used in certain portions of the examples: BA= butyl acrylate; EA= ethyl acrylate; AA=acrylic acid; MAA=
methacrylic acid; AN= acrylonitrile; MMA= methyl methacrylate; BGDMA=
1,3-butylensglycol dimethacrylate; BMA = butyl methacrylate; IM=
polyisobutylane; St=styrene; BR= elastomeric poly(butadiene); NR =
natural rubber.

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p!eparation of a two-phase Dol~rn~ with fiv~
~arts of a second çross-linked ~hase A monomer emulsion was prepar~d of the following ingredients:

Water 435 3 Sodium lauryl sulfate (28%) 27.7 9 Butyl acrylate 1353.7 g Acrylonitrile 103.8 g Methacrylic acid 24.5 g This emulsion was added in 5 shots to a vessel containing 645 g water and was conducted at 50C and polymerized using a redox system consisting of 2.28 9 cumene hydroperoxide and 1.54 g sodium sulfoxylate formaldehyde. After completion of the reaction, 78 g of butyleneglycol dimethacrylate was added and polymerized with 1.0 g t-butylhydroperoxide and 0.5 g isoascorbic acid. A sample of the emulsion was precipitated via tre0zing.
The dried sample was milled and presssd into a 1/8" she0t. Oth0r characteristics of the polymer are presented in Exampl~ 2.

EXAMeL~2.
Preparation o~three-~hase polym~r with 15 parts o~ a hard outer phase (Tg of final phase c~, 57C?

An emulsion was prepared in the same manner as in Example 1 excep~ that a third phase was added in a one-shot mode consisting of 220.2 g methyl methacrylate and 55.1 g butyl acrylate and polymerized with 0.23 g sodium persulfate and 0.23 g sodium formaldehyde sulfoxylate. The precipitated and dried resin was milled and molded as in Expl.1. The following physical properties were obtained:
Tensile Max. Elong. at break Tg k~m2 ~ C
Expl. 1 1 1.3 312 -26 Expl. 2 46.6 720 -24 An Instron Tensile Tester was used to measure free-film mechanical properties. Films were cast in polypropylene petri dishes and allowed to dry at least two weeks. The film thickness was 0.09-0.10 cm. If required, films were frozen to separate from the clish and/or talc was applied to facilitate handling. A die was used to cut a dog-bone shaped sample having 0.64 cm width in the thin area. The ends were wrapped with masking 1ape before being clamped in the Instron jaws.
The following parameters were used in th0 Instron tester Crosshead speed: 2.54 cm/min.
Initial gap: 1.27 cm In general, samples were run in duplicate.

Data reported are:
Tensile (max.) - the highest stren~th observed Tensile (break) - the tensile strength when the sample breaks Elong,ation (max.) - the elongation at tensile maximum Elongation (break) - the elongation when the sample breaks EXAMPLE 3.
~ two-ehaS~ actylic polymer witb five part~

Examples 3 and 4 demonstrate that the presence of a hard thermoplastic outer phase allows achievement of acceptable tensile properties with a first phase having a lower glass temperature. A 5-gallon reactor was charged with 8000 g water and heated to 55C. A monomer emulsion was prepared in another vessel consisting of: 22~0 g water, 390 9 Siponate DS-4, 1596 g butyl acrylate, 7286.5 9 butyl methacrylate and 142.5 9 methacrylic acid.A seed was prepared in situ by adding 583 9 of the monomer emulsion and initiating it with 5 ~ of a 1% aqueous solution of ferrous sulfate, followed by 100 g of a solution of 18 ~ sodium persuifate in 500 g water and 100 g of a solutionof 15 g sodium bisulfite in 500 9 water. After the exotherm, the remaining monomer emulsion was added gradually over ca. 2.5 hours together with the remaining solu~ions of the persulfate and bisulfite maintaining the reaction temperature at 65i3C. A 30 min. hold followed the end of feeds, after which thereaction was cooled to 45C and 475 g of butyleneglycol dimethacrylate was added followed by solutions of 3~4 g t-butylhydroperoxide in 50 g watet and of rJ ; ~ J

2.5 g isoascorbic acid in 50 g waier. The rea~ion was held for 20 minutes after the reaction reached its peak. A sample was precipitated by freezing, washed and dried. The calculated Tg of the first-phase polymer was +1 C.

EXAMeL~
A thre~-phase all-acrylic polymer with 15 parts Qf a hard ou~er Rh~
A 5-gallon vessel was charged with 8000 9 water and thoroughly deaerated. A monomer emulsion was prepared consisting of 2000 g water, 351.1 g Siponate DS-4, 2422.5 g butyl acrylate, 5531.4 g butyl methacrylate and 121.1 g methacrylic acid. The vessel was heated to 55C and a seed was prepared in situ by adding 520 ~ monomer emulsion and initiating it with 100 g of a solution of 16.15 g of sodium psrsulfatH in 500 g wat0r followed by 100 9 of a solution of 13.75 g sodium bisulfite in 500 g water and 5 g of a 1% aqueous offerrous sulfate. ASt0r the exotherm, the remaining monomer emulsion was added gradually over 2 hours together with the r0maining solutions of sodium persulfate and sodium bisulfite. The reac~ion temperature was maintained at 65 i2C. A hold period of 30 min. followad the end of the feeds after which the reaction was cooled to 45C, 425 g of butyleneglycol dimethacrylate was added and initiated with solutions of 3 g t-butylhydroperoxide in 50 g water and 2.5 gisoascorbic acid in 50 g water. The reaction was kept for 30 minutes after which1200 g methyl methacrylate and 300 g butyl acrylate was added and initiated wHh solutions of 1.5 g sodium persulfate in 75 g water and of 1.~5 g sodium formaldehyde sulfoxylate in 75 g water. After a hold of 30 minutes, a sample was precipitated by freezing, washed and dried. The glass tsmperature of the first-plhase polymer was calculated as -9C. It was noted that films from polymers containing butyl methacrylate in the first phase were less prone to exhibit whitening on exposure to water at temperatures of 70 or above.
The sarnples of Examples 3 & 4 were milled and molded into 1/8 "
sheet!; and the following physical properties wer~ obtained:
Tensile Elong. at Break Tg ~m2 % oc Example 3 91.0 325 18 Example 4 85.2 318 6 EXAMPL~ 5 The use of th~ third phaS~UQws one to improve both tensile strength ~nd iower tha glass temp~rature of the multi-pha~d pQl~r.

A monomsr emulsion was prepared consisting of 2241 g water, 64.8 g Siponate DS-10, 5265 g butyl acrylate, 2673 g methyl methacrylate and 162 g of m0thacrylic acid. A reaction v~ssel containing 6840 g water was deaerated and a solution of 16.2 g Siponate DS-10 in 54 g water was added.
The vessel was heated to 55C, 728 y of the monomer emulsion prepared above was placed in the reactor and initiated with 90 g of a solution of 16.2 g sodium persulfate in 630 g water, 90 g of a solution of 13.5 g sodium bisulfite in 630 g water and 13 g of a 1% aqueous solution of ferrous sulfate. After the exotherm, the remaining monomer emulsion was added gradually over a 3 hours period together with the remaining solutions of sodium persulfate and sodium bisulfite maintaining the reaction temperature at 65 ~2C. A 1/2 hour hold followed the end of feeds afler which the reactor was cooled to 45C, 426 gof butylenQglycol dimethacrylate was added and initiated with solutions of 3 g t-butylhydroperoxide in 45 g water and of 2.2 g isoascorbic acid in 45 9 water.
A~er a 1/2 hour hold, the reaction was cooled. A sample was precipitated by freezing, washed and dried.

A monomer emulsion was prepared consisting of 2000 g watar, 351 g Siponate DS-4, 5650 9 butyl acrylate, 2301 9 methyl methacrylate and 121 g methacrylic acid. A reaction vessel containing 8000 9 water was deaerated with a nitro3en sparge, heated to 55C and 520 g of the prepared monomer emulsion was added. It was initiated with 100 9 solutions of each, 16.2 g sodium persulfate in 500 9 water, 13.7 g sodium bisulfite in 500 g water and with 5 g of a 1% aqueous solution of ferrous sulfate. After the exotherm, the remaining monomer emulsion, persulfate and bisulfite soiutions were added gradually over a 2.5 hours penod maintaining a reaction temperature of 65 i2C. A 1/2 hour hold followed the end of the feeds. The reaction was cooled to 45C, 425 g of butyleneglycol dimethacrylate was added and initiated with solutions of 3 g t-butylhydroperoxid~ in 50 g water and of 2.2 g isoascorbic acid in 50 g water. After a hold of 30 minutes, 1200 9 methyl methacrylate and 300 g butyl acrylate was added and initiated with aqueous solutions of 1.5 3 sodium persulfate and of 1.25 g sodium formaldehyd~ sulfoxylate. After 30 minutes, the reaction was cooled, a sample was precipitated by freezing, washed and dried.
The samples of examples 5 & 6 were milled and molded and the following physical propsrties were obtained:

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Tensila.kg/cm2 Elong. a~kreak. % :~
Example 5 54.5 535 4 Example 6 82.3 450 -3 The procedure of Example 1 was followed to prepare an emulsion of butyl acrylate/ acrylonitrile/ acrylic acid = 91.6/ 7/ 1.4. The reaction was concluded prior to the addition of any crosslinking monomer. The particle size in Examples 7-10 was set by the addition to the initial aqueous phase of 64 ~ ofa 45% solids seed polymer; said seed polymer was approximately methyl methacrylate/ butyl acrylate/ methacrylic acid 49/50/1 and of particle size ca.
100 nanometers.

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The procedura of Example 1 was followed to prepare a two-phase polymer of butyl acrylate/ acrylonitrile/ acrylic acid// butylene glycol dimethacrylate = 97( 91.6/ 7/ 1.4)// 3.

EX~
The emulsion of Example 7 (400 parts, 59.7~h solids) was further reacted by addition of a monomer emulsion of:
Parts Butyl acrylate 21.1 Methyl methacrylate 20 Methacrylic acid 1.05 Siponate DS-4 anionic surfactant 0.19 Water 1 0 at 50C, followed by addition of 0.055 parts of t-butyl hydroperoxide and 0.036 parts of isoascorbic acid ~as 5% aqueous solutions). The reaction exothermed to 59C. A second aWition of similar amounts of initiator was made in 1 minutes. The resulting solids content was 60.3%. The calculated glass temperature of the outer phase was +4C. and of the first phase was -47C.

The latex of Example 8 (391.5 grams at 61% solids) was treated with the outer phase monomer mix in the proportions and amounts of Example 9 to form a three-phase polymer.

~AMPLE ~ 1 This example compares the properties of the polymers of Examples 7 ~o 10 to illustrate the improved balance of properties imparted by the final harder phase. Values of tensile strength and elongation were measured at room temperature.

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phase phase Soluble Swelling Tensile Elongation Il. ~Q iU. % Fraction Ratio Strenglh S~ m2~ (o/Q) 7 0 0 93 a 1.5 1717 8 3 0 37 22 5.9 91 0 9 0 1 5 75 67 13.6 1882 1 0 3 1 ~ 34 20 26.7 1 200 a - Too lightly crosslinked to measure EXAMPL~
Three-pha~ PQ~m~f~lLfor damping in blonds witb a thQrmosettable rubber.
The process of Example 2 was used, except that the ratio of monomers was altered slightly to produce a multi-phase polyrner of Phase l//Phase IVPhase lll= 79.3//4.2//15, wherein Phase I is BA/AN/SV MM=
90.8/7.0/0.6/1.6; Phase ll is BGDMA 100; Phase lll is MMAIBA = 80/20. A small amount of a polymer seed of ca. 80 nm size, composition BA/MMA/AA -49.5/49.5/1, was added prior to the initial polymerization. The resulting latex was coagulated by tha techniques taught by Frankel et al cited herein of single-unit coagulation, liquid dewatering, and e~trusion, and extruded into 3 mm pellets. Similar results will be obtained if the polymar is coagulated by freezing, washing the gumstock with water, squeezing the gumstock free of water, and drying in vacuo, as the subsequent compoundin~ does not require the thermoplastic elastomeric polymer to be in pellet form.

EXAI\/IeLEI 3 This example illustrates the praparation of a three-phase polymer baseà on a polymer of somewhat higher glass tamperature, wherein no seed was employed. The process of Example 2 was used, except that the ratio of monomers was alterad slightly to produce a polymer of Phase l//Phase ll/Phase 111= 80.8114.21115, wherein Phase I is BAJBMA/ MAA= 30.0/68.5/1.5; Phase 11 is BGDMA 100; Phase 111 is MMA/BA = 80/20. The polymer was isolated as in Example 12.

E~MPLE 14 This example illustrates a polymer similar to that of Example 4 but without a third thermoplastic phase. The process of Example 4 was followed, except the step of polymerizing the third phase was omitted. The polymer was isolated by the rnethod of Example 12. The polymer has a weight r~tio of Phase 1// Phase 11 of 951/5; Phase I is BA/BMA/MM= 17.7/80.7/1.6; Phase 11 is BGC)MA
100.

MPLE 1~
This example illustrates the preparation of a two-phase polymer of Tg ca. 25C. The process of Example 4 was followed, except the step of polymerizing the third phase was omitted. The polymer was isoiated by the method of Example 12. The polymer has a weight ratio of Phase 1// Phase il of 95//5; Phase I is BA/MMA/MAA= 50.0/48.5/1.5; Phase 11 is BGDMA 100.

The process of Example 1~ was repea~ed to yield a ~wo-phase polymlsr of Tg ca. 0C. The polymer has a weight ratio of Phase 11/ Phase 11 of 95115; Phase I is BA/MMAIMAA= 65.0/33.0/2.0; Phase 11 is BGDMA 100.

~2~MPL~
This example illustrates the damping propertiss of the two- and three-phase polymers of the previous examples. Materials from certain of the above preparations after isolation by either precipitation or extruder coagulation were processed into appropriate test specimens by pressing in a Carver press between Mylar polyester spacers at 180C platen temperature for 2 to 3 minutes at 1.38 x 109 dynes/square crn (piston pressure), then cooling to 1 5C and pressing for 4 to 5 minutes at 6.9x1 Oô dynes/square cm (piston pressure).
Spacer plates were used to obtain thicknesses of 3.175 mm for dynamic mechanical testing or 0.51 mm for tensile and elongation testing. Room temperature tensile properties were determined to show that acceptable strength and elongation were obtained, and that the degree of tension set or physical recovery was not excessiva. The glass temperature was dstermined by differential scanning calorimetry.
The dynamic mechanical values are measured on a Rheometrics Dynamic Spectrometer (Rheometrics Instruments, Piscataway, NJ), equipped with rectangular tooling torsion fixtures. Samples of the acrylic two- or three-phase polymer are compression molded and cut into strips of 63.5 mm length by 12.7 mm wide by 3.2 mm thickness. The sample is dried ov0might at 60C in vacuo, and then affixed to the jaws of the spectrometer. The sample is cooled to -1 40C. A maximum strain of only 0.4% is utilized until the test temperature is above that of the onset of rubbery properties; at no time does the maximum strain exceed 10%. Measurements are made at 20C intervals over a frequency sweep of 0.1 to 200 radians/second. The maximum temperature may be as high as 1 40~C but usually these polymers be3in to exhibit obvious viscous flow at the highest temperature and the geomstry is not maintained.
The plots obtained of tan ~ vs. frequency at each temperatUrQ are then superimpcsed, utilizing the Williams-Landel-Ferry equation (J D Ferry, Viscoelastic Proper~ies of Polymers, Chapter 13, John Wilay and Sons, New York, 3rd edition, 1980). From the master plot of tan ~ vs. Iog frequency is determined the frequency range in decades over which tan ~ exceeds 0.4.

Tensile Polymer of Tg, Strength, Elongation, Ma~imum Range, E~m~le t~ Isil~Pascals % Tan ~ Decades 12 -20 6900 800 0.8 4 13 + 5 7280 300 0.8 4 14 +20 9660 300 1.4 6 1~ +25 13800 200 1.5 6 16 0 4800 500 1.4 6 This example illustrates ~he excellent damping behavior and fatigue life of three compositions, A, B, and C, mada according to the invention as compared to those of a composition D, which was not made according to the invention. Compositions A, B, and C comprise the two-phase acrylic thermoplastic elastomeric polymers from Examples 15, 16, and 14, respectively, incorporate~ in the thermosettable elastomer formulation shown below. In these formulations, the two-phase acrylic thermoplastic elastomeric polymers above were used as the additive polymer and X = 60. The raference composition D incorporates polyisobutylene (IM) as the additive polymer and X = 20. Phr= parts per hundred of cross-linkable elastomer.

~omposltioll F~m~iQn p~rN~
SMR-L (Natural Rubber) X
Bromobutyl Rubber 100-X
Additive Polymer 20 Carbon Black 35 (N-660) Stearic Acid 2 Zinc Oxide 5 Paraffinic Petroleum Oil 5 ASTM Type 1 04B
Diphenylamine Derivative 1.5 2- and 3- Methyl 1.5 Mercaptobenzimidæole Thiocarbamyl Sulfenamide 1.20 N-Oxydiethylene Benzothiazole .55 2-Sulfenamide Elemental Sulfur 0.40 The first three ingredients (the polymeric components) were combined and mixed in a laboratory-size (model BR) Banbury mixer for 1.5 minutes. The ramaining ingredients exclusive of accelerators and sulfur were added in two portions and the mixture masticated for a total of 6.0 minutes. It was then dumped from the Banbury, sheeted with a rubber mill, and allowed to cool. Curatives (accelerators and sulfur) were subsequently added to 5509. of the mix~ure on a rubber mill according to ASTM D3182, with no pre-conditioning of the carbon black.
The materials were molded according to ASTM D~182 and cured to 100% optimum as determined by Monsanto oscillating disc rheometer.
Cure ~emperatures were varied for different moldings of the same formulation to optimize fatigue properties. The cure tamperatures listed in Table I were optimal for each formulation.
Ultimate tensile strength and elongation at brcak were determined under ambient conditions according to ASTM D412 (dis C) and tear strength according to ASTM D624 (die B). An electromechanical tester was used at a t0st speed of 500 mm per minute.
Compression set testing was done according to ASTM D395 (method B). The tsst specimens were held undsr 25% compression for 22 hours at 125C in ventilated, air-circulating oven, and a 30 minute relaxation at room temperature was allowed before taking final measurements. Testing for mechanical fatigue was conducted either as taught by Tabar (more fully described by Lemieux et al.), or by test method ASTM D4482-85 using a Monsanto fatigue-to-failure tester.
Dynamic-mechanical propGrties including tan ~ and glass transition temperature (Tg) were dsterminsd on a Polymer Laboratories DMTA. Isochronal (10Hz) data was collected in simple tension from -100 to 100C, at a strain dispiacement of 62 microns, and a heating rate of 2C/minute. Isothermal data was collected on simple shear specimens over frequencies of 0.01-100 Hz at 20C intervals from -20 to 1 00C.

TABL~ 18-2 t: ompositi~n ~itiV9 Polymar Çuro Temp~L~re. C

A Exampls 15 140 B Example 16 140 C Example 14 140 The compositions containing the two-phase acrylic thermoplastic elastomers have comparable or improved fatigue resistance compared to the reference composition containing polyisobutylene. Tha comparison of log (fatigue life), as cycles, against lo~ (strain energy) (mJlmm3) was ploned~ and the numbers in Table 18-3 were derived using linear regression. All lhrae of the compositions according to this invention (A, B, and C) havs improved fatigue resistance over the referenca composition (D3 at test energies up to 630 mJ/mm3. The composition containing the additive polymer from Example 16 had the best fatigue life over the entir~
range of the test.

Fatigue Resistan~ of BIQnds A. B. C. and D

Strain Energy Lo~ Fatigue Life. cycles mJ/ mrn~
400 -- 5.75 5.63 5.56 600 5.75 5.46 5.31 5.30 700 5.40 5.35 5.19 5.21 1000 5.26 5.10 4.91 4.98 1150 4.83 5.00 4.80 4.89 1400 4.67 4.86 4.65 4.77 The isochronal (10 Hz) tan ~emperature response for these compositions are presented in Table 1~-4. All three compositions according to the invention display more uniform damping behavior over the temperature range of -50 to -20C as compared to that o7 the reference composition. Also, the same three formulations, A, B, and C, provide much improved damping behavior over that of the reference composition in the temperature range from 0 to 20C, especially so for 7Ormulations B and C.

TABLE 1 ~
isoC~r~ m~9 Response fo! CompositiQns A. B. ~and D
I~3rature. ~C Ian ~ for CQnnposiions -55 0.28 0.24 0.43 0.46 -50 0.55 0.52 0.63 0.9~
-40 0.83 0.69 0.64 0.97 -20 0.71 0.57 0.53 0.69 0 0.31 0.32 0.30 0.30 +20 0.17 0.30 0.29 0.14 This improved damping behavior was confirmed using ambient response of the formulations. Table 18-5 is taken from the experimentai plot of tan ~l log frequency (H~).

T~BL~ 5 Damping Response f~r ~omposition~ B. C. and D
at Various Frequencies at T = 20C
Frequ~ncy. I Iz ~n ~ fQr~mpositions D
0.01 0.15 0.12 0.16 0.08 0.10 0.11 0.15 0.18 0.07 1.0 0.10 0.17 0.18 0.08 10.0 0.16 0.21 0.22 0.14 50.0 0.28 0.31 0.29 0.26 It was also found that inclusion of the multi-phase acrylic elastom~rs in the compositions imparts higher values of tan ~ over a wide range of test fr0quencies. At 80C similar behavior is obscrved, except at the very iow frequencies where tan ~ is nearly the same for all formulations.

TA~LE 1 8-~
Damping Response for CO~QS~S A. B. C. and D
at Various Fre~u~ s at T = 80Ç
Frequency. Hz tan ~ for Com~Qsitions B C ~2.
0.10 0.09 0.10 0.09 0.08 1.0 0.09 0.10 0.09 0.~7 10.0 0.11 0.10 0.11 0.07 50.0 0.16 0.12 0.15 0.09 100.0 0.19 0.15 0.19 0.11 Table 18-7 is a comparison of the physical properties of the compositions. The effect of varying the additive polymer is negligible, except for a slight lowering of the tensile strength for Sampl~ A and a slight improvement in compression set for Sample C.

s`;
h~ ;J .: ~ J ` .' _ Physical PrQp~ QmParis~n SamplQ Tensil~Elongation Tear% Compression ~e~ % StrenathSet A 15.0 548 53.1 36.5 B 17.4 598 ~6.4 34.6 C 17.3 613 60.8 33.4 D 18.2 680 54.8 35.4 This example illustrates ths exeell0nt damping behavior and fatigue life of a eomposition E made aeeording to the invention as compared to that of composition D, the reference composition made in Example 18. Composition E comprises the three-phase acrylic thermoplastie elastomer from Example 12 in the thermosettable elastomer formulation shown in Example ~8. The three-phase acrylic polymer was incorporated as the additive polymer with X = 60. Sample E
was mixed and molded aocording to the procedure of Example 18 and cured at a eure temperature of 170C. A eomparison of the isoehronal tan ~ behavior for tha two formulations is shown balow. As ean bs seen from these data, eomposition E whieh comprises the three-phass aerylic polymer displayed a mora uniform damping response as eompared to that of referenc6 composition D over the temperature range of -~0 to -20C, and surpassed the damping of referenee eomposition D over the range of -15 to 20C.

iA) ~i 1 ' ~ ! ~

IaE~L~:l Temperature. C tan E for Com,oQsitions ~2 -55 0.46 0.40 -~0 0.92 0.66 -40 0.97 0.68 -20 0.69 0.56 0 0.30 0.37 0.14 0.17 ~eL~2~

This example illustrates the expected excellent physical properties of a composition according to this invention. The composition is made according to the formulation and procedure of Example 18 except that the bromobutyl rubber is replaced by 25 phr of polybutadisne rubber (BR). This composition includes a multi-phase acrylic thermoplastic elastomer, such as taught in Example 16. The heat-aged physical properlies of this formulation would be expected to be superior to those of typical NR damping materials due to the inclusion of the polybutadiene rubber in the composition. Tabar et al in U.S. Patent 4,362,840 disclosed the improvement of heat aging properties afforded ela-~tomeric compositions of NR, BR and IM. The improved damping behavior of examples 18 and 19 over formulations containlng IM is fully expected to be analogous to this example, and should provid~ an advantag3 in applications where higher heat rasistance is necessary. Due to the thermoplastic naturs of the multi-phase acrylic polymers, and therefore the lower viscosity relative to most elastomers under high-shear mixing temperatures, the fatigue-rasistance-enhancing discrete particle morphology will be present in this formulation.

E2~D~eL~
This example makes a dir~ct comparison between a composition utilizing a multi-phase acrylic elastomer as the additive polymer and a compositionally analogous formulation utilizing IM as the additive polymer. Sample B, previously described, was used as the composition containing the multi-phase acrylic elastomer. Sample F was prepared with IM as the additive polymer in the formulation of Example 18-1 with X
= 40 and Y= 20, and cured at 1 70C.
Dynamic measursments were taken with a Rheometrics RMS 800 mechanical sp~ctrometer at 25C and 100C using the parallel plate geometry. Data was collected and recorded at rates from 1 to 100 radians/sec., and the samples were placed under 15% compression to prevent slipping.
Values from the plotted data are shown in Table 21-1. Sample B
exhibits an improved tan ~ response over the entire range of frequencies in comparison with the prior art sample, and ~he trend is maintained at high temperaturs.

C~omparison of Damping Behavior of Composition Containing Multi-Phase Acrylic Polymer with One Containin~ Isob~ylene Polymer Rate ofDamping ~tan S ) of Msasursment,Formulated/Cured Compounds radians/sec. 13. 25 F. 25 B~100 F. 100 0.22 0~21 0.14 0.14 6 0.26 0.22 0.15 0.13 0.27 0.22 0.15 0.13 22.5 0.31 0.24 0.15 0.12 0.33 0.25 0.15 0.12 0.36 0.27 0.15 0.12 100 0.39 0.30 0.15 0.12 While the invention has been described with reference to specific examples and applications, other modifications and uses for the invention will b~ apparent to those skilled in the art without departing from the spirit and scope of the invention defined in the appended ciaims.

Claims (13)

1. A process comprising using for damping purposes a multi-phase, thermoplastic elastomeric polymer having at least two polymeric phases comprising:
a) an initial linear or lightly crosslinked polymeric phase polymerized from an a,.beta.-ethylenically unsaturated monomer, wherein said a,.beta.- ethylenically unsaturated monomer comprises from 0 to about two percent by weight of multi-ethylenically unsaturated monomer, b) a second polymeric phase in the form of discrete domains of about 2 to about 50 nanometers in diameter dispersed within said initial polymeric phase, wherein said second polymeric phase is polymerized from at least one ethylenically unsaturated monomer comprised of about 5 percent to 100 percent by weight multifunctional monomer having at least two sites of ethylenic unsaturation, wherein the weight ratio of said second polymeric phase to said initial polymeric phase plus said second polymeric phase is from about 1:100 to about 1:2.

2. The process of claim 1 wherein said multi-phase thermoplastic elastomeric polymer further comprises a final polymeric thermoplastic phase whose glass temperature is greater than that of said initial polymeric phase, a portion of said final polymeric phase being intimately attached to at least one of said initial and said second polymer phases.

3. The process of claim 2 wherein said multi-phase thermoplastic elastomeric polymer further comprises particulate filler.

4. The process of claim 1 wherein said multi-phase thermoplastic elastomeric polymer further comprises particulate filler.

5. A composition for useful damping purposes comprising:
a) crosslinked elastomer containing microscopically discrete segments of b) multi-phase thermoplastic elastomeric polymer having at least two polymeric phases comprising:
1) an initial linear or lightly crosslinked polymeric phase polymerized from an a,.beta.-ethylenically unsaturated monomer, wherein said a,.beta.- ethylenically unsaturated monomer comprises from 0 to about two percent by weight of multi-ethylenically unsaturated monomer, 2) a second polymeric phase in the form of discrete domains of about 2 to about 50 nanometers in diameter dispersed within said initial polymeric phase, wherein said second polymeric phase is polymerized from at least one ethylenically unsaturated monomer comprised of about 5 percent to 100 percent by weight multifunctional monomer having at least two sites of ethylenic unsaturation, wherein the weight ratio of said second polymeric phase to said initial polymeric phase plus said second polymeric phase is from about 1:100 to about 1:2.

6. The composition of claim 5 wherein said multi-phase thermoplastic polymer further comprises a final polymeric thermoplastic phase whose glass temperature is greater than that of said initial polymeric phase, a portion of said final polymeric phase being intimately attached to at least one of said initial and said second polymer phases.

7. The composition of claim 5 further including reinforcing particulate matter.

8. The composition of Claim 5 wherein said crosslinked elastomer is selected from a group consisting essentially of natural or synthetic polyisoprene, elastomeric butadiene, and bromobutyl rubber.

9. The composition of Claim 8 further including reinforcing particulate matter.

10. The composition of Claim 9 wherein said composition comprises as said crosslinked elastomer a blend of said polyisoprene and said bromobutyl rubber in a weight ratio of from about 100:1 to about 0.65:1 and, said crosslinked elastomer being crosslinked by a curative comprising a curing agent selected from the group consisting of sulfur, isocyanate, and blocked isocyanate.

11. A process comprising use of the composition of claim 10 for damping.

12. A process comprising use of the composition of claim 5 for damping.

13. A process comprising use of the composition of claim 6 for damping.